What is needed in the art is a film cartridge which will indicate whether the film in the cartridge has been exposed.
Recently there has been a desire by snap-shooters, photo enthusiasts, and professionals to be able to determine if a roll of film has been advanced through a camera or has never been used. This can be accomplished by attaching an exposed film indicator to the long end of the spool on a 35 mm cartridge. This is primarily needed when shooting multiple rolls of film, or for the purpose of some consumer and professional cameras, when a roll is only partially exposed to be used again later.
One problem involving assembling the exposed film indicator to the cartridge, is developing a method to reliably attach two thin disks to the long hub end of the spool. The inner (or exposed) disk is attached to the spool hub by three barbs and therefore rotates with the spool. The word EXPOSED may be printed on it, or to differentiate from the outer disk, it may be a different color. The outer (or unexposed) disk is attached to the crimp diameter of the end cap. It remains stationary relative to the cartridge. The word UNEXPOSED may be printed on it, or, again to differentiate from the inner disk, it may be a different color. When a customer purchases a fresh roll of film, the outer disk on the exposed film indicator will be visible. As film is wound back into the cartridge after the pictures are taken, a tab that sticks up on the inner disk engages a tab that sticks down on the outer disk. The inner disk then exits through a slot in the outer disk and is visible to the customer.
U.S. Pat. No. 5,708,879 shows a film cartridge with a visual exposure status indicator.
U.S. Pat. No. 5,715,494 is another example of a film cartridge with a visual exposure status indicator.
To implement adding exposure indication to a 35 mm film cartridge in a timely and cost effective manner, it is necessary to minimize the impact on the existing manufacturing infrastructure. Given the complexity of this infrastructure and the space constraints around the equipment, it is highly desirable to add the feature after the film cartridge is completely assembled. Since the completed film cartridge is loaded into the canister at the end of the film winding operation, the feature must be assembled to the cartridge either by removing the cartridge from the canister or while the cartridge is in the canister. It is advantageous to assemble the feature to the film cartridge while it is in the canister since:
1) The canister provides a convenient method of conveying and singulating the film cartridges for the assembly operations. PA0 2) It is difficult to reinsert the film cartridge back into the canister without using a special motion to wrap the film leader around the cartridge. PA0 3) Reduced handling of the cartridges and thus the potential for cosmetic damage to either the cartridge or the film leader is reduced. PA0 4) Equipment space limitations does not permit cartridge removal.